1. Field of the Invention
The present invention relates to a mobility management node in an IP packet communication system, a paging area forming method carried out by the mobility management node, and a mobility management program executed by a computer in the mobility management node.
2. Related Background Art
In Mobile IP and its extended systems, in order for a mobile node to receive packets addressed thereto, even with changeover of its connected network from a home network to another network, the mobile node transmits a binding update packet (BU: Binding Update packet, which will be referred to as “BU”) to a home agent (HA: Home Agent) at every change of its connected network. For decreasing the number of BUs, a paging area is used. The “paging area” is an area in which, where the mobile node is not under communication, the mobile node transmits no BU even with migration between networks within a certain region. As long as the mobile node is within the paging area, it transmits no BU to HA. However, the mobile node need transmit a BU even in a non-communication state if it goes out of the paging area. Therefore, in order to decrease the number of BUs, it is necessary to properly set the paging areas.
A conventional method of forming the paging areas was that in which a mobile node successively stored records of base stations passed, or stored changes of geographical locations by means of GPS, managed migration patterns of its own, and notified a node in a network of data associated with the migration patterns. In another method, each mobile node was configured so that at every handoff between base stations the mobile node notified a newly connected base station of information about a previously connected base station before a handoff (e.g., cf. Japanese Patent Application Laid-Open No. 2001-251660). A node in the network created a paging area on the basis of the information thus notified of by the mobile nodes and notified the mobile nodes of information about networks included in the paging area.